U.S. patent number 6,951,114 [Application Number 10/619,936] was granted by the patent office on 2005-10-04 for reliable outdoor instrument cooling system.
This patent grant is currently assigned to Weatherford/Lamb, Inc.. Invention is credited to John N. Grisham, Michael M. Meadows, Leslie Wayne Perry, Alan J. Sallwasser.
United States Patent |
6,951,114 |
Grisham , et al. |
October 4, 2005 |
Reliable outdoor instrument cooling system
Abstract
A method, system, and apparatus for controlling the temperature
within a remotely located enclosure that contains temperature
sensitive equipment is provided. For some embodiments, the system
includes an array of thermoelectric cooling (TEC) devices that act
as an active cooling device and an active heating device. The
system may also include a temperature controller that receives
signals from a temperature sensor located at or near the
temperature sensitive equipment. The controller may be configured
to supply DC power to the thermoelectric coupling devices based on
the output signal of the temperature sensor. The polarity of the DC
power can be reversed by the controller in order to cause the
thermoelectric device to heat or to cool the enclosure. The system
also contains a passive cooling device. The system includes an
independent electrical power source with a battery and solar cell
to supply power to the temperature control devices and the
equipment contained in the enclosure.
Inventors: |
Grisham; John N. (Houston,
TX), Meadows; Michael M. (Cypress, TX), Perry; Leslie
Wayne (Southington, CT), Sallwasser; Alan J. (Houston,
TX) |
Assignee: |
Weatherford/Lamb, Inc.
(Houston, TX)
|
Family
ID: |
32908870 |
Appl.
No.: |
10/619,936 |
Filed: |
July 15, 2003 |
Current U.S.
Class: |
62/3.7;
62/259.2 |
Current CPC
Class: |
F25B
21/02 (20130101); F25B 27/002 (20130101); G05D
23/1919 (20130101); H01L 35/00 (20130101); F25B
2321/0212 (20130101); F25B 2700/2104 (20130101); F25D
2700/16 (20130101) |
Current International
Class: |
F25B
21/02 (20060101); F25B 27/00 (20060101); G05D
23/19 (20060101); H01L 35/00 (20060101); F25B
021/02 () |
Field of
Search: |
;62/3.2,3.3,3.6,235.1,259.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Electronic Enclosures, EIC Solutions, Inc., May 30, 2003, pp. 1-2.
.
Peltier Thermoelectric Coolers, Circuit Cellar Online, May 30,
2003, pp. 1-15..
|
Primary Examiner: Jones; Melvin
Attorney, Agent or Firm: Moser, Patterson & Sheridan,
L.L.P.
Claims
What is claimed is:
1. An apparatus for regulating temperature of one or more
temperature-sensitive components within a main enclosure,
comprising: a self-contained power supply; one or more
thermoelectric coolers; a temperature sensor for measuring
temperature within a temperature-controlled zone at or near the
temperature-sensitive components; an inner enclosure within the
main enclosure, the inner enclosure made of a thermally conductive
material that is thermally coupled to the thermoelectric coolers;
and a temperature controller configured to regulate power supplied
from the independent power supply to the thermoelectric coolers to
maintain the temperature within the temperature-controlled zone
within a specified range by conduction between the thermoelectric
coolers and the inner enclosure.
2. The apparatus of claim 1, wherein the self-contained power
supply comprises one or more batteries.
3. The apparatus of claim 2, wherein the apparatus further
comprises one or more solar cells adapted to charge the one or more
batteries.
4. The apparatus of claim 1, wherein the temperature controlled
zone is defined by the inner enclosure.
5. The apparatus of claim 1, further comprising one or more heat
exchangers thermally coupled with the thermoelectric coolers.
6. The apparatus of claim 5, wherein the inner enclosure is
thermally coupled to the one or more heat exchangers via the
thermoelectric coolers.
7. The apparatus of claim 6, wherein contact surfaces of the inner
enclosure thermally coupled with the thermoelectric coolers are
spaced to minimize regions of high temperature in the heat
exchangers.
8. The apparatus of claim 6, wherein the temperature-sensitive
components are thermally coupled to the inner enclosure with a
thermal interface material.
9. The apparatus of claim 1, further comprising an insulative
material disposed within the main enclosure.
10. The apparatus of claim 5, wherein the heat exchangers are
attached to exterior walls of the main enclosure.
11. The apparatus of claim 1, wherein the temperature controller is
configured to regulate power supplied from the independent power
supply to the at least one thermoelectric cooler by varying a duty
cycle of a pulse width modulated signal.
12. The apparatus of claim 1, wherein the temperature controller is
configured to: supply the thermoelectric coolers with a voltage
signal having a first polarity to cool the temperature-sensitive
components; and supply the thermoelectric coolers with a voltage
signal having a second polarity, opposite the first polarity, to
heat the temperature-sensitive components.
13. The apparatus of claim 1, further comprising a thermal switch
responsive to a temperature within the temperature controlled zone,
wherein power is removed from the at least one thermal electric
cooler in response to the thermal switch changing states.
14. The apparatus of claim 1, wherein the controller is configured
to maintain the temperature of the temperature-sensitive components
at or above an anticipated dewpoint for a geographic area in which
the apparatus is deployed or is to be deployed.
15. An apparatus for regulating temperature of one or more
temperature-sensitive components within a main enclosure,
comprising: a self-contained power supply; one or more
thermoelectric coolers; a temperature sensor for measuring
temperature within a temperature-controlled zone at or near the
temperature-sensitive components; and a temperature controller
configured to regulate power supplied from the independent power
supply to the thermoelectric coolers to maintain the temperature
within the temperature-controlled zone within a specified range,
wherein the apparatus is capable of maintaining a temperature
within the temperature controlled zone within a range of
approximately 0.3 degrees Celsius peak to peak within a predefined
target temperature.
16. An apparatus for maintaining a temperature of one or more
temperature-sensitive components within a main enclosure,
comprising: one or more solid state cooling devices; a thermally
conductive manifold that is thermally coupled to the one or more
solid state cooling devices to conduct heat from the
temperature-sensitive components to the solid state cooling
devices; a temperature sensor for measuring temperature at or near
the one or more temperature-sensitive components; and a temperature
controller configured to generate a signal to the solid state
cooling devices to maintain the temperature at or near the
temperature-sensitive components within a specified range.
17. The apparatus of claim 16, wherein the manifold is thermally
coupled to one or more heat exchangers on the exterior of the main
enclosure, via the one or more solid state cooling devices.
18. The apparatus of claim 16, wherein the manifold is shaped to
minimize convective transfer of heat from the manifold to the
interior of the main enclosure.
19. The apparatus of claim 18, wherein the manifold comprises one
or more protrusions, each having a contact surface shaped to mate
with one of the solid state cooling devices, wherein the
protrusions are configured to evenly distribute heat among fins of
the heat exchangers.
20. A fiber optic sensing system, comprising: one or more fiber
optic sensors for sensing one or more downhole parameters; one or
more optical signal processing components optically coupled to the
one or more fiber optic sensors via one or more optical fibers; and
a temperature controlled enclosure housing the one or more optical
signal processing components, one or more thermoelectric coolers
thermally coupled via at least one thermally conductive manifold
with at least one of the optical signal processing components, a
temperature sensor for measuring temperature at or near the optical
signal processing components, and a temperature controller
configured to vary power supplied to the thermoelectric coolers
based on a signal from the temperature sensor.
21. The system of claim 20, wherein the temperature controller is
configured to vary power supplied to the thermoelectric coolers by
varying a duty cycle of a pulse width modulated signal.
22. The system of claim 20, wherein the temperature controller is
configured to supply the thermoelectric coolers with a voltage
signal of a first polarity to cool the temperature-sensitive
components and a voltage signal of a second polarity, opposite the
first polarity, to heat the temperature-sensitive components.
23. The system of claim 20, further comprising one or more heat
exchangers disposed on an exterior of the enclosure and thermally
coupled to the thermoelectric coolers.
24. The system of claim 23, wherein the thermoelectric coolers are
spaced to evenly distribute heat across fins of the heat
exchangers.
25. The system of claim 24, wherein the at least one thermally
conductive manifold comprises a plurality of protrusions, each
having a contact surface for mating with a corresponding
thermoelectric cooler.
26. The system of claim 20, further comprising a thermal interface
material disposed between the optical signal processing components
and the thermally conductive manifolds.
27. The system of claim 20, further comprising: a bank of one or
more batteries for supplying power to components within the
enclosure; and an array of one or more solar panels for maintaining
a charge on the bank of one or more batteries.
28. The system of claim 27, wherein the array of one or more solar
panels is positioned to shade the enclosure.
29. A method of regulating temperature of one or more
temperature-sensitive components within an enclosure, comprising
the steps of: thermally coupling the temperature-sensitive
components to one or more thermoelectric coolers via at least one
thermally conductive manifold; measuring temperature at or near the
temperature-sensitive components; and varying power supplied to
thermoelectric coolers thermally coupled with at least one of the
temperature-sensitive components, in response to the measured
temperature.
30. The method of claim 29, further comprising thermally coupling
the thermoelectric coolers to one or more heat exchangers disposed
on an exterior of the enclosure.
31. The method of claim 29, wherein varying power supplied to
thermoelectric coolers in response to the measured temperature
comprises performing a proportional-integral-differential control
algorithm, using the measured temperature as feedback.
32. The method of claim 31, wherein varying power supplied to
thermoelectric coolers comprises varying a duty cycle of a pulse
width modulated signal.
33. The method of claim 29, wherein varying power supplied to
thermoelectric coolers in response to the measured temperature
comprises: applying a voltage signal of a first polarity to the
thermoelectric coolers to cool the temperature sensitive
components; and applying a voltage signal of a second polarity to
the thermoelectric coolers to heat the temperature-sensitive
components, wherein the second polarity is opposite the first
polarity.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an enclosure for housing
electronic equipment and, more particularly, to a
temperature-controlled enclosure for housing remotely located
temperature sensitive equipment, such as optical signal processing
components for monitoring downhole parameters in oil wells.
2. Description of the Related Art
Electronic equipment produces heat when operated and, when the
equipment is located in an environment with extreme ambient
temperatures, some means of controlling the temperature of the
equipment is typically required. Certain electronic equipment, such
as opto-electronic components used in optical signal processing are
especially sensitive to temperature variation and require an
operating temperature in a relatively narrow range in order to
function properly. In the oil production industry, such optical
signal processing components, located in a control panel at a
wellbore surface, are often used in conjunction with downhole fiber
optic sensors to measure various downhole parameters.
Often, such control panels are located in remote locations of the
earth and subjected to extreme temperatures, which may subject the
components to temperatures in excess of their preferred operating
temperature range. It is important the maximum operating
temperature is not exceeded in order to prevent damage to the
component. Further, some components used in measurement systems,
especially those that have very low signal to noise ratios (e.g.
capacitive based systems), may suffer degradation in accuracy and
resolution due to changing ambient temperatures at the front end of
their signal conditioning. Such changes in ambient temperatures
naturally occur, for example, between day and night. Therefore,
controlling both the stability of the temperature and its magnitude
are highly desirable.
Heat generated within the panels may be passively removed, but as
the ambient (outside) temperature increases, cooling by passive
means becomes less effective. Therefore, in order to compensate for
extreme heat, devices such as fans and liquid coolers may be used
in order to cool sensitive electronic equipment. However, neither
approach is satisfactory if the temperature of the device must be
below the outside air temperature. Therefore, in such cases, a
device which can produce temperatures below the surrounding air
temperature, such as a compressor based refrigerator, is
required.
However, cooling systems utilizing refrigerators and fans contain
many moving parts and are, therefore, subject to mechanical
failure. For example, refrigerating compressor components are
subject to mechanical failure and typically require frequent
maintenance, However, remotely located control panels are generally
required to operate essentially unattended for long periods of time
and frequent maintenance is inconvenient and expensive,
particularly if production operations are interrupted.
Additionally, cooling systems using refrigerators require
substantial power to drive the compressor and typically require a
reliable external source of electrical power (e.g., line AC
service), which is often not available in remote locations.
Accordingly, a need exists for a temperature controlled electrical
enclosure that can operate in a remote environment with minimal
maintenance, and, preferably, without an external source of
reliable electrical power.
SUMMARY OF THE INVENTION
The present invention relates to an apparatus for and method of
controlling the temperature of an electrical enclosure in a remote
location.
One embodiment provides an apparatus for regulating temperature of
one or more temperature-sensitive components within a main
enclosure. The apparatus generally includes a self-contained power
supply, one or more thermoelectric coolers, a temperature sensor
for measuring temperature within a temperature-controlled zone at
or near the temperature-sensitive components, and a temperature
controller configured to regulate power supplied from the
independent power supply to the thermoelectric coolers to maintain
the temperature within the temperature-controlled zone within a
specified range.
Another embodiment provides apparatus for maintaining a temperature
of one or more temperature-sensitive components within a main
enclosure. The apparatus generally includes one or more solid state
cooling devices, a thermally conductive manifold positioned to
conduct heat from the temperature-sensitive components to the solid
state cooling devices, a temperature sensor for measuring
temperature at or near the one or more temperature-sensitive
components, and a temperature controller configured to generate a
signal to the solid state cooling devices to maintain the
temperature at or near the temperature-sensitive components within
a specified range.
Another embodiment provides a fiber optic sensing system. The fiber
optic sensing system generally includes one or more fiber optic
sensors for sensing one or more downhole parameters, one or more
optical signal processing components optically coupled to the one
or more fiber optic sensors via one or more optical fibers, and a
temperature controlled enclosure housing the one or more optical
signal processing components, one or more thermoelectric coolers
thermally coupled with at least one of the optical signal
processing components, a temperature sensor for measuring
temperature at or near the optical signal processing components,
and a temperature controller configured to vary power supplied to
the thermoelectric coolers based on a signal from the temperature
sensor.
Yet another embodiment prvides a method of regulating temperature
of one or more temperature-sensitive components within an
enclosure. The method generally includes thermally coupling the
temperature-sensitive components to one or more thermoelectric
coolers, measuring temperature at or near the temperature-sensitive
components, and varying power supplied to thermoelectric coolers
thermally coupled with at least one of the temperature-sensitive
components, in response to the measured temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates an exemplary application environment in which
embodiments of the present invention may be utilized.
FIG. 2 is a perspective view of an enclosure, according to one
embodiment of the present invention.
FIG. 3 is a relational top view of an enclosure, according to one
embodiment of the present invention.
FIG. 4 is a diagram of an exemplary array of thermoelectric cooling
(TEC) devices, according to one embodiment of the present
invention.
FIG. 5 is a detailed relational view of a temperature-controlled
inner enclosure and attached TECs, according to one embodiment of
the present invention.
FIG. 6 is a perspective view of one embodiment of the inner
enclosure of FIG. 5.
FIG. 7 illustrates the maintained temperature within the inner
enclosure that may be achieved by one embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention generally provides methods, apparatus and
systems for controlling the temperature in an enclosure suitable
for housing temperature sensitive components. For some embodiments,
cooling systems of the present invention may utilize thermoelectric
cooling (TEC) devices. TEC devices are particularly appropriate for
this application because they contain no moving parts and require
little maintenance relative to compressor based refrigerators and
cooling systems utilizing fans. For some embodiments, the cooling
systems may also include a self contained power source operable in
remote locations of the earth (e.g., locations without reliable
electrical power).
Embodiments of the present invention may be utilized to an
advantage to maintain the operating temperature of virtually any
type temperature-sensitive equipment, such as analog electronic
components, high speed digital electronics, components with very
low signal to noise ratios_or any other type of components.
However, to facilitate understanding, embodiments of the present
invention may be described below with reference to maintaining the
operating temperature of temperature sensitive opto-electronic
components as a particular, but not limiting, application example.
Accordingly, it should be understood that the following techniques
described with reference to opto-electronic components may also be
applied to other types of temperature-sensitive components, as
well.
An Exemplary Application Environment
FIG. 1 illustrates an exemplary fiber optic sensing system 100
having a temperature controlled enclosure 130, according to one
embodiment of the present invention. As illustrated, the enclosure
130 may house optical signal processing components 135 in
communication, via at least one connecting line 136, with one or
more fiber optic sensors 137 deployed as part of a string of
production tubing (pipe) 110 within a wellbore 120. The fiber optic
sensors 137 may include any combination of well known fiber optic
sensors, for example, utilizing fiber Bragg grating (FBGs),
interferometers, and/or distributed temperature sensing (DTS), to
sense any combination of a wide variety of downhole parameters,
such as temperature, pressure, flow, vibration, density, and the
like.
The optical signal processing components 135 may include any
suitable combination of optical, electronic, and/or opto-electronic
components suitable for interrogating the fiber optic sensors 137,
such as a light source, optical components for receiving light
reflected from the fiber optic sensors 137, and opto-electronic
components for converting the reflected light into electrical
signals provided to a main controller 134. For some embodiments,
one or more the optical signal processing components 135 may be
thermally coupled directly to the active temperature regulating
components 139. For other embodiments, one or more of the optical
signal processing components 135 may be thermally coupled with the
active temperature regulating components 139 via a thermally
conductive inner enclosure 138 housing the optical signal
processing components 135. The inner enclosure 138 may act as a
manifold conducting heat away from the optical signal processing
components 135 to the temperature regulating components 139.
The inner enclosure 138 may define a temperature-controlled zone,
the temperature in which is maintained by the temperature
regulating components 139, in conjunction with a temperature
controller 132. For example, the temperature controller 132 may
generate a control signal, based on a temperature sensor (not
shown) thermally coupled with the optical signal processing
components 135 and/or located within the inner enclosure 138, to
vary an amount of cooling or heating by the temperature regulating
components 139 in order to maintain the temperature in the inner
enclosure 138 within a predefined range. The predefined range may
vary with different embodiments, and will generally be chosen to
ensure accurate operation of the optical signal processing
components 135. In other words, the predefined range will typically
fall within a specified operating range of the optical signal
processing components 135 (or any other type equipment contained
within the inner enclosure 138).
While the inner enclosure 138 generally provides the highest level
of temperature control within the main enclosure 130, the remaining
components (e.g., main controller 134 and temperature controller
132) also receive the benefit of cooling or heating from the
exterior walls of the inner enclosure 138.
As shown in FIG. 1, for some embodiments, such as embodiments used
in remote, offshore or difficult to reach locations, a solar panel
105 (or array of solar panels) supplies electrical power to a bank
of one or more battery(s) 106 which in turn supplies electrical
power to the enclosure 130 via a cable 107, thus enabling operation
of the control panel 130 in such locations without reliable
electrical service. The solar panel 105 may also be strategically
placed to provide shade to the enclosure 130, which may further
assist in its cooling. In other embodiments, the solar panel 105
and/or battery(s) 106 may be replaced, or supplemented, with
another power source such as a generator, fuel cell, wind machine
or other electrical energy-producing device. In some embodiments,
line AC power may be used to operate the apparatus if such power is
available.
FIG. 2 shows an exterior view of one embodiment of the enclosure
130 with a cut-away section exposing the internal enclosure 138. As
illustrated, because the enclosure 130 may be deployed in remote
locations, operating unattended and exposed to the elements, the
enclosure 130 may be sealed from the elements (e.g., hermetically
sealed). Sealing of the enclosure 130 may exacerbate the problems
of heating due to heat generating components, such as the optical
signal processing components 135, as there is no convective path
for the heated air to escape. Therefore, as illustrated, the inner
enclosure 138 may be thermally coupled to heat exchangers (e.g.,
one or more finned heat sinks 140) located on the exterior of the
enclosure 130. Additionally, due to the sealed nature of the
enclosure, a desiccant material may be included to prevent
condensation of the moisture contained in the air trapped inside
the enclosure 130.
FIG. 2 shows the arrangement of the heat sinks 140 and 141 present
in the preferred embodiment, but any of the heat sinks may be
located on any of the exterior walls of the enclosure as required
by the components inside the enclosure 130.
Relational View of the Temperature-controlled Enclosure
As illustrated by the arrows 143 in the relational view of the
enclosure 130, shown in FIG. 3, heat generated by the optical
signal processing components 135 may be conducted to the finned
heat sink 140, via the inner enclosure 138 and the active
temperature regulating components 139 as shown by arrow 151. In
other words, the inner enclosure 138 may be made of a thermally
conductive material (e.g., metal) and may have an inner surface
shaped to thermally couple to the optical signal processing
components 135. As illustrated, the inner enclosure 138 may also
include protrusions 144 having a surface shaped for thermally
coupling with the active temperature regulating components 139.
As previously described, the temperature controller 132 may be
configured to control the active temperature regulating components
139 via one or more control signals generated based on a signal
received from a temperature sensor 133. The temperature sensor 133
may be generally positioned to monitor the temperature of the
optical signal processing components 135 or, more generally, the
temperature within the inner enclosure 138. The temperature
controller 132 may be implemented using any suitable components,
such as a dedicated "off the shelf" temperature controller, a
specially configured embedded controller, programmable logic
controller (PLC), or any other suitable type controller. Further,
while shown as separate components, for some embodiments, the main
controller 134 may be configured to perform the temperature
controlling algorithms described herein, eliminating the need for a
separate temperature controller.
The temperature controller 132 may be configured to implement any
suitable known or to be developed control algorithm (e.g., using
the signal from the temperature sensor 133 as feedback), such as
simple On/Off control, proportional (P) control,
proportional-derivative (P-D) control, or
proportional-integral-derivative (P-I-D) control, to generate a
signal suitable for controlling the active temperature regulating
devices 139. The control signal generated may be any type suitable
to control the type of active temperature regulating devices 139
chosen for a given application. Examples of suitable control
signals include voltage signals, current signals, and frequency
signals.
For some embodiments, the active temperature regulating components
139 may include thermoelectric cooling TEC devices, and the control
signal may be a modulated DC signal. For some embodiments, cooling
and/or heating with the TEC devices may be controlled by varying
the duty cycle of a pulse-width-modulated (PWM) DC signal, in order
to vary the DC power supplied. TEC devices operate on the Peltier
principle: as direct current (DC) passes through a junction of two
dissimilar metals, one metal evolves heat, while the other absorbs
heat. As shown, the TEC devices may be disposed between the inner
enclosure 138 and the finned heat sink 140 (e.g., with a different
one of the dissimilar metals thermally coupled to each). Thus, by
regulating the DC power supplied, the TEC devices may be
configured, in effect, as a heat pump, drawing heat from the inner
enclosure 138 to the finned heat sink 140. This effect is reversed
when the direction of the DC current is reversed (e.g., the
polarity of the DC signal is reversed), which may result in
delivery of heat to the optical signal processing components
135.
Thus, the TEC devices 139 may provide a convenient means for both
heating and cooling, as required. It should be noted that the TEC
devices 139 are, generally more efficient at heating and,
therefore, less power is typically required for heating purposes.
Conveniently, while more power is generally required for cooling
with the TEC devices 139, there is also generally more sunlight at
times when cooling is necessary. The solar panels 105 are generally
designed to be able to maintain sufficient charge on the bank of
batteries 106 powering the panel in expected lighting conditions
throughout the year.
For some embodiments, the inner enclosure 138 may be shaped in
order to enhance the ratio of heat transfer via conduction vs. heat
transfer to the interior of enclosure 130 via convection. The inner
enclosure 138 is heat conductive and is in contact either directly
or via thermal grease 142 or other known or to be developed thermal
interface material with one or more TEC device 139 or other active
cooling or heating devices known or to be developed. Particularly,
the inner enclosure 138 may have protrusions 144 with a contact
surface shaped substantially similarly to the contact area of the
thermoelectric cooler(s) 139.
As illustrated in FIG. 4, the TEC devices 139 may be arranged as an
array in contact with the heat sinks 140 mounted on a wall of the
enclosure 130. The positions of the TEC devices 139 in contact with
the heat sink 140 may be optimized to minimize the concentration of
heat (hot spots) in the heat exchanger 140 in order to maximize
overall heat transfer. In other words, the TEC devices 139 may be
located to evenly distribute (spread) heat among fins of the heat
sink 140 to maximize the transfer of heat to the surrounding
ambient air.
The TEC devices 139 may be connected electrically in any suitable
arrangements. As shown, for some embodiments, sets of
parallel-connected TECs may be connected in series. The exact
electrical configuration is a design decision and may be based on
several factors, such as the exact type and size of TECs used,
available power, the required amount of heating and/or cooling, the
required accuracy (e.g., how broad a temperature range must be
maintained), and the like. These and other factors may be
considered by a designer to arrive at an optimal physical and
electrical arrangement of TEC devices 139.
In some cases, failure of the temperature sensor 133 and/or
temperature controller 132 may have catastrophic results, for
example, causing the TECs to heat rather than cool, which may cause
permanent component damage. Further, it may also be possible for
the TEC devices 139 to become decoupled from the inner enclosure
138 and/or heat sink 140, in which case, the conductive path from
the optical signal processing components 135 to the outside may be
broken, preventing the TEC devices 139 from efficiently cooling. As
the temperature rises (e.g., as indicated by the temperature sensor
133), the temperature controller 132 may then continue to increase
power to the TEC devices 139, which may eventually damage the TEC
devices 139. Therefore, for some embodiments, a thermal switch 150
may be utilized to monitor temperature within the inner enclosure
138, or otherwise within the main enclosure 130. For example, the
main controller 134 may be configured to detect the opening of the
thermal switch 150 and take appropriate responsive action (e.g.,
disconnect power to the optical signal processing components,
disregard readings, alert service personnel, etc.).
Referring back to FIG. 3, other heat sinks 141 may be positioned in
close proximity to other heat generating components inside the
enclosure 130, such as the main controller 134. This allows heat
transfer, as shown by arrow 148, to the environment in localized
high temperature areas while preventing heat transfer from outside
the enclosure 130 to the inside of the enclosure in areas that have
a temperature lower than the outside air temperature. Additionally,
insulation 149 may be disposed within the enclosure 130, for
example, in an effort to reduce the amount of unwanted heat
transfer between the environment and the enclosure.
As shown in FIG. 5, for some embodiments, a contact surface of
protrusions 144 of the inner enclosure 138 may be shaped to mate
with a surface of the TEC devices 139. To enhance thermal
conductivity (i.e., reduce thermal resistance) a thermal interface
material (TIM) 142, such as a thermal grease, thermal adhesive, or
thermal epoxy, may be disposed between the protrusions 144 and the
TEC devices 139. Similarly, while not shown in the figures, a TIM
may also be disposed between the TEC devices 139 and the heat sink
141.
FIG. 6 shows the inner enclosure 138 split into its component
parts. The surfaces 146 and 147 may or may not mate as is permitted
by the size and shape of the temperature sensitive component
located in the temperature controlled zone. In other words, for
some embodiments, rather than fully enclose the optical signal
processing components 135, the inner enclosure 138 may merely
contact the optical signal processing components 135. In either
case, as previously described, the inner enclosure 138 acts as a
manifold, of sorts, conducting heat from the optical signal
processing components 135 to the TEC devices 139.
FIG. 7 contains graph 700, a chart of temperature within the
temperature controlled inner enclosure 138 versus temperature
within an environmental test chamber (i.e., an oven), showing the
effectiveness of the temperature control that can be achieved with
one embodiment of the present invention. As shown, while the
chamber temperature is varied from approximately 46.degree. C.
(115.degree. F.) to approximately 26.degree. C. (79.degree. F.),
the temperature within the inner enclosure 138 may be maintained
within 0.3.degree. C. of a target temperature (as shown,
approximately 20.degree. C.). An even tighter range may be
achieved, for example, by optimizing control parameters (e.g.,
P-I-D parameters) of temperature controller 132.
Typically, a range of 0.5.degree. C. will be sufficient for
opto-electronic components. It will be appreciated that, for some
embodiments, wider (or otherwise different) temperature ranges may
be predefined depending on the requirements of the particular
components housed in the inner enclosure 138 (e.g., digital
electronic components may be able to operate within a wider
temperature range than optical signal processing components
135).
Further, the temperature range may be centered around a higher or
lower target temperature, for example, in an effort to reduce power
consumption. As an example, maintaining a target temperature of
30.degree. C. may require less power for cooling than maintaining a
target temperature of 20.degree. C., due to the smaller difference
from the outside temperature. Additionally, a target temperature
may be selected above the anticipated dew point of the ambient air
in order to prevent condensation of humidity in the air inside the
enclosure 130.
Conclusion
By maintaining the temperature of one or more temperature-sensitive
components within an enclosure, embodiments of the present
invention may improve the accuracy of measurements made using such
components. By utilizing a combination of conduction via active
solid state cooling devices and passive convection (e.g., via heat
sinks), operating temperatures may be maintained within a specified
range without moving parts, which may reduce the frequency of
associated maintenance. Further, the reliability of some components
may degrade over time, as a function of ambient temperature. Thus,
by maintaining such components (or subsystems containing them) at
cooler temperatures, the reliability and longevity of a whole
system may be improved.
While the foregoing is directed to embodiments of the present
invention, other and further embodiments of the invention may be
devised without departing from the basic scope thereof, and the
scope thereof is determined by the claims that follow.
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